The following U.S. Pat. Nos. exemplify the state of the art of selectively self-sealing drain valves: 4,103,372, 3,771,177, 3,428,295, 3,380,081, 3,366,980, 2,173,529.
It is well known in the prior art to provide sealable drain valves in large plumbing installations such as bathtubs, roman tubs, and the like. Because of the size of these fixtures, it is often difficult to install self-sealing drains having a remote actuator which is linked to the drain itself via a lever or chain arrangement extending beneath the tub. The most popular form of sealable drain valve which does not require a remote actuator is a pop-up drain fitting, such as the one shown in U.S. Pat. No. 4,144,599, issued Mar. 20, 1979, to Casper Cushera. However, pop-up drain fittings are not suitable to large tub installations such as roman tubs, due to the fact that the drain is often placed in a central portion of the bottom of the tub, in a position where the bather is likely to sit or recline. All prior art pop-up drain fittings are constructed so that the drain sealing cover extends substantially above the plane of the tub surface in which the drain fitting is secured. As a result, the drain cover may interfere with the bather in the tub, and might easily cause injury to the bather. Also, the drain sealing cover of a pop-up drain fitting is often released from the sealed position by the application of slight force to one side of the drain cover. There is a great likelihood that a pop-up drain fitting as known in the prior art often would be inadvertently released and opened by a bather sitting or reclining on or near the pop-up drain fitting.